Did Foot-and-Mouth Disease-Control Operations Affect Rodenticide Exposure in Raptors?

Second generation anticoagulant rodenticides in predatory birds: Probabilistic characterisation of toxic liver concentrations and implications for predatory bird populations in Canada

“…A sometimes cited -toxicity threshold‖ is given as -greater 33 than 0.1 -0.2 mg/kg wet weight‖ (Newton et al 1998). This was, in 34 fact, described as a -potentially lethal range‖ and was derived for a single species, the 35 barn owl (Tyto alba); it stems from two sets of observations (Shore et al 2001). Firstly, 36 barn owls diagnosed post-mortem as having died from rodenticides had liver 37 concentrations > 0.1 mg/kg.…”

“…In the French Department of Loire Atlantique, 73% of a sample consisting of 321 common kestrels (Falco tinnunculus), common buzzards (Buteo buteo), barn owls and 16 322 tawny owls (Strix aluco) had detectable SGAR liver residues (Lambert et al 2007). In the 323 UK, between 40% and 74% of barn owls, kestrels, and avian scavengers such as buzzards 324 and red kites (Milvus milvus) found dead from various causes had detectable liver SGAR 325 residues Shore et al, , 2006Walker 2008b). However, it 326 should be noted that the sampled areas of Canada were those with higher population 327 densities and where landscape features are not greatly dissimilar from Europe.…”

Second generation anticoagulant rodenticides in tawny owls (Strix aluco) from Great Britain

“…The proportion of individuals with liver SGARs in these species varies between 40% and 70 % (Newton et al, 1999;Shore et al, 2000;Shore et al, 2006). However, the frequency of occurrence of SGARs in tawny owls was broadly similar to that of a mammalian predator, the weasel Mustela nivalis that, like tawny owls, feeds predominantly on Apodemus spp.…”

“…Raptors in which relatively widespread exposure has been documented in Britain include the barn owl (Tyto alba), buzzard (Buteo buteo), red kite (Milvus milvus), and kestrel (Falco tinnunculus) (Newton et al, 1999;Shore et al, 2000;Shore et al, 2006). The liver concentrations in many individuals are relatively small and are thought to reflect sublethal exposures, but larger residues have been found in some individuals and SGARs diagnosed as the likely cause of death (eg., Barnett et al, 2005Barnett et al, , 2006Barnett et al, , 2007.…”

Long-term trends in mercury and PCB congener concentrations in gannet (Morus bassanus) eggs in Britain

“…Although, PCB and Hg contaminant concentrations are reported to have fallen in some terrestrial and aquatic biota during the 1970s and 1980s, concentrations after 1990 appear to have levelled off or may even be increasing (Cifuentes et al, 2003;Simpson, 2007;Walker et al, 2007). One of the long term biomonitors of contaminant levels in marine systems around Britain has been gannet (Morus bassanus) eggs (Newton et al, 1990;Alcock et al, 2002;Shore et al, 2005). A previous study on eggs collected up until 1987 from colonies off both the Atlantic and North Sea coasts of Britain revealed a decline in Hg conc entrations in two colonies (including Ailsa Craig) but a significant increase in four colonies (including Bass Rock) (Newton et al, 1990).…”